Variable voltage divider

ABSTRACT

A variable voltage divider having a ceramic substrate supporting a plurality of resistive paths and comprising an arcuate resistive path disposed between two fixed resistive paths, the fixed resistive paths being abraded to achieve a proper resistance ratio between each of the two fixed resistor paths and the arcuate resistive path, a plurality of terminations, a center collector, and a driver mounted in a center aperture in the substrate and carrying a contactor, the contactor wipingly engaging the collector and the arcuate resistive path. The ceramic substrate is enclosed in a housing and contains registration means for locating the substrate in the housing, the two fixed resistive paths being arcuately disposed about said registration means.

United States Patent 1 Rozema et al.

[ 1 VARIABLE VOLTAGE DIVIDER [73] Assignce: CTS Corporation, Elkhart,Ind.

[22] Filed: ()et. 31, 1973 [21] App]. No.: 411,400

[52] US. Cl. 338/48; 338/163; 338/164; 338/184; 338/199 [51] Int. Cl.HOIC 10/34 [581 Field of Search 338/48, 128, 68, 118, 162, 338/163, 164,174. 184. 199

1 1 Sept. 30, 1975 3,448,427 6/1969 Baskett 338/162 3,585,559 6/1971Rozema et al. 338/48 3,662,317 5/1972 Digiaolama et al 338/174 PrimaryE.\'a mincrBruce A. Reynolds [57] ABSTRACT A variable voltage dividerhaving a ceramic substrate supporting a plurality of resistive paths andcomprising an arcuate resistive path disposed between two fixedresistive paths, the fixed resistive paths being abraded to achieve aproper resistance ratio between each of the two fixed resistor paths andthe arcuate resistive path, a plurality of terminations, a centercollector, and a driver mounted in a center aperture in the substrateand carrying a eontactor, the eontactor wipingly engaging the collectorand the areuate resistive path. The ceramic substrate is enclosed in ahousing and contains registration means for locating the substrate inthe housing, the two fixed resistive paths being arcuately disposedabout said registration means.

10 Claims, 4 Drawing Figures U.S. Patent Sept. 30,1975 3,909,769

FIGURE-2 FIGURE-3 FIGURE- 4 YARIABLE VOLTAGE DIVIDER The inventionrelates generally to voltage divider controls and more particularly tocontrolsthat-are particularly suitable for .use as variable voltagedividers.

Variable voltage dividers such asdisclosed-in U.S. Pat. No. 3,585,559,assignedto the sa rneassignee as the present invention, generallycomprise a=substrate containing three resistive paths, a collector, acontactor wipingly engaging one of the resistive paths and thecollector, a driver for changing the position of theucontactor relativeto the resistive paths, and a pluralityof ,termination means forconnecting the voltage divider with the circuitry of suitable electronic apparatus. The termination means include a highvoltage .inputtermination, a low voltage or ground ,terniinatiomand anoutputtermination. The resistive paths include an arcuate resistivepath,,afixed resistive path connected to themcuate resistive path andacurrentlimiting resistive path interconnecting th e collector and theoutputtermination. H i I More sophisticated electronic equipment requires thatthe voltage dividersbe rnore compact physically and geometrically aswellasbe able, to handle much higher voltages. Specifically, in oneapplication, variable voltage dividers are used to supply a constantvoltage to the focus electrode of cathode ray tubes. In this advances inpicture tube technologyra DC voltage in the range of 8,300 10,500 voltsis now connected to the input of the voltage'divider. This hasnecessitated the use of additionalelectrical'resistance in the'form ofanadditional resistive path, in-the voltage divider circuit to achieve asuitable voltage at the'output termina tion. In addition, someapplications-require thatthe additional circuitry required to controlthe higher voltages be compressed onto asmaller substrate thanheretofore' required. It would therefore be'desirable to pro vide avariable voltage divider capable'of cohtrolling increased power supplyvoltages: and yet smaller and more compact than prior art voltagedividers;

Another problem with prior art controls'such as disclosed .in the abovementioned patent, was-the exposureof the control to the. environment.Thus metal-objects or particles could comeinto contact with the voltagedivider and short out thecontrol. Inadd'ition, due to the high voltagescarried by the voltage divider, a serious safety hazard existed duringthe maintenance and servicing of the .electronic equipment containingthevoltagedivider. It wouldvtherefore be desirable :to provide. a variablevoltage divider that minimizespotential shorting out of the control aswell as-providing aidivider. 1 that eliminates the safetyhazardthatexists during the equipment .ccn taining the servicing .of theelectronic voltage divider.

Afndther problem-in prior arltj'varia ble. voltagedividers was that theresistance values. of each of the .resistive paths had to be held toacceptable toleranees in order toobtain the required outputvoltages-This3.";

often resulted in rejection of the entire voltage divider.-

changes in *itheformulati'on of the resistive material, changesinatmospheric conditions during the screening or application oftheresistive material to the substrate, changes in thefiring. cycle of theresistive material, and changesin the configuration of the resistivepath such as path thickness. Asa result,'the inability of even one of,the various resistive pathsto meet ,the tolerances ,abrading ofparticular resistivepaths after the resistive paths have been. screenedOnthe substrate and fired.

;The present invention comprises an arcuate resistive. path connectedbetween two fixed resistive paths with.

one of the fixed resistive paths. connected to the .input voltage, theother fixedresistive path connected to a low voltag e or ground, andthegou tput voltagetaken from the arcuate resistive path. Rather thanattempting to apply theresistive paths with relatively close toleranceshowever, the two fixed resistive paths are applied to the substrate at aresistance value substantially lower than norrnally required. To achievea desired output voltage for a given input voltage, it is only necessarythat the ratio of the resistance of each of the fixed resistive paths tothe resistance of the arcuate resistive path be at a predeterminedvalue. Regardless of the absolute value of each of the resistive paths,if the ratios equal the predetermined value, the outputvoltage will bein the proper range. Therefore, after the resistive paths have beenscreened on the substrate and fired, portions of each of the fixedresistive paths are abraded t'o increase the resistance and to obtainthe predetermined ratioQThiS procedure establishes the desired range ofoutput voltage values as well as permits a much'wider range'of tolerancein the screening of the resistive paths. This has resulted in asubstantial increase in produc'tion yield. It would therefore bedesirable to produce a variable'voltage divider that could obtain adesiredoutput voltage range without the necessity'of'holding the variousresistive paths to close tolerances'and it'would be desirable to produce21 voltresistive path'sin alignmentbn opposite sides of thearcuaterresistive -'path and wherein the fixed resistive pathsareabrad'edto achieve a predetermined ratio of the resis'tance'fof eachfixed resistive path to the resis tance of the arcuate'resistive path. Afurther object of I the present invention is'to provide a-nw andimproved be 'very difficult due to the many factors thatcan affect theresistance value of a resistance path such as.

voltage dividercontaining a housing with a center aperture. and locatorpins, a substrate with registration meansfor locatingthe substrate in"the housing and actuatingmeans secured to said substrate and having aknob portion extending-through the center aperture of the .housing. Afurther object-of the invention is to provide a substrate containing acenter-aperture and registratiommeans,and'wherein' the arcuate resistivepath is disposed about the center aperture and the fixed resistive pathsare disposed about said registration means.

Further objects and advantages of the present invention will becomeapparent as the following description proceeds, and the featurescharacterizing the invention will be pointed out with particularity inthe claimsannexed to and forming a part of this specification.

Briefly, the present invention is concerned with a variable voltagedivider having a ceramic substrate supporting a plurality of resistivepaths on a surface thereof, the resistive paths comprising an arcuateresistive path connecting two fixed resistive paths, a contactor driveroverlying said surface and having a shaft porat one end of the fixedresistive paths including a termitance value of the arcuate resistivepath.

For a better understanding of the present invention reference may be hadto the accompanying drawings wherein the same reference numerals havebeen applied to like parts and wherein:

FIG. 1 is an isometric view of a variable voltage divider built inaccord with the present invention;

FIG. 2 is a sectional view taken along the line IIll of FIG. I;

FIG. 3 is an exploded isometric view of the variable voltage divider ofFIG. 1; and

FIG. 4 is a plan view of the contactor driver assembled to the substratein accord with the present invention.

The conductive pads or terminations 27, 28 and 29 are preferablycomprised of a film of palladium gold or other suitable solderableconductive material that would form a good electrical connection withthe material used to make the resistive paths. The same material mayalso be used for the collector 22 and may be applied in any suitablemanner, e.g., by screening. By making the resistive paths 14, l6, 18, 20from a common cermet formulation and by applying these paths to a commonsurface 134 of the substrate 12, variations occurring in the processingof the resistive paths such as variations in the pressures used whileapplying the resistive paths to the surface of the substrate orvariations in firing time or temperature will have substantially anidentical effect on each of the resistive paths. Hereinafter theconductive pad 27 will be referred to as the input termination, theconductive pad 28 will be referred to as the low potential or groundedtermination, and the conductive pad 29 will be referred to as the outputtermination.

The housing further contains a surface 50 containing 9 grooves 52, thesurface 44 containing a recess 48 join- Referring now to FIGS. I through4, there is illus- I trated a variable voltage divider generallyindicated by the numberal 10 comprising a housing 40 formed ofthermo-plastic or othersuitable dielectric material, a

. substrate 12 formed of a dielectric material such as alu mina or glassand containing a first surface 130 and a second surface 13b spaced apartfrom and parallel to surface 13a, the surface 13a supporting resistancemeans in the form of a first resistive path 14, a second resistive path16, a third resistive path 18 and a fourth resistive path 20, andsupporting a conductive collector 22 and a plurality of conductive padsor terminations 27, 28 and 29 with a plurality of terminals 30 connectedthereto. The substrate 12 further contains a-' ing each of the grooves52'at the intersection of surface 44 with surface 50, As best seen inFIGURE 2 there cesses 48 and grooves 52 allow the terminals 30 to extendthrough terminal holes 36 and wrap around a portion 39 of the substrate12 without impeding a secure fit of the substrate 12 within the housing40. Each of the terminals 30 contains a back portion 70 located in arecess 48, a bottom portion 72 located in a groove52f and a clip portion74 causing the terminal 30 to wrap around a portion 39 of substrate 12,a solder deposit 76 electrically connecting the terminals 30 to theconductive pads. The housing 40 also contains a mounting pin aconductive contactor 21 trapped and resiliently com- I pressed betweenthe planor surfaces 13a of the sub-,

' strate l2 and 37 of the contactor driver 23, the contacdriver with thesubstrate by projecting through the cen-. ter'aperture 32 in thesubstrate 12. As best illustrated in FIG. 2, an end 26a of the stubshaft 26 is enlarged by heat swaging and forms a bearing 26b against asurface 13b of the substrate. The contactor driver 22 also includes theknurled adjusting shaft 31 that facilitates manual adjustement of thedivider, the shaft 31 extending through aperture 42 in the housing 40.In order to space the driver 23 from the surface of the sub strate andto provide for smooth adjustment of the con- 1 trol, a bearing 33 isprovided on the surface 37 of the driver 23.

.the surface 38 spaced apart from the parallel to surface 37. Asseen inFIG. 3, the housing 40 contains a circular receptacle 49 for receivingthe contactor driver 23. the receptacle49 defined by-sannular wall51.=A.surface 56 defines thebottom of receptacle 49 and receptacle 49contains another-surface 54elevated withrespect to surface '56,thesurfa'ces 54 and 56 defining a passageway 58'. Whenthe driver isassembled in :the housing, the surface 38. of'the driver abuts thesurface 54 of the housing, the stop arm .5 being disposedin passageway58. Abutment surfaces GOand 61 form the endsofpassageway 58 and engagestop arm 35 as-t-he stop arm is rotated by the-driver 23 to the limitsofpassageway. 58, thus halting the rotational movement.of,.the driver 23.

The variable voltage divider is formed by first applying the resistivepaths on the substrate, firingthe substrate, then applying theconductive pads and firing-the substrate again. Fixed resistive paths,14 and 18 are then abraded so that the ratio of the resistance of eachof the paths 14 and l 8 tothe resistance of the arcuate resistive path 16 is a predetermined value. Asseen in FIG. 4', the resistive pa th l6isdisposed intermediate the fixed resistive paths 14 and 18 the resistivepath 16 being circularly disposed about theicenter aperture 32 and eachof the fixed're sistive paths l4 and 18 being disposed about one of thefloc atoiyholes34 respectively. One end of the. iresistive 'path 1 8 is,connec'ted to the input termination 27 and oneend of the resistive path14 is connectedto the ground termination 28,:the output termination29-.being connectedto fixediresistiv'e path '20. For agivelnyoltdge'inputis longasthe resisnmc'e ratios of the p'aths14and stotiie ath '16 equal predeterr'nined'valu es, theoiitput 'voltagerangeover the limits of the arcu'ate resistive path 16 will be constantregardless of the absolute v alue' of the resistive paths 1451- and is.Thereforefthe rfesistiveipaths 14 and 18 are applied to thestibstrate ata valii e g'enerally lower than required.

After the resistive paths and conductive pads have been applied to thesubstrate and fired, each of the resistive paths l4 and 18 is abraded.The removal of portions of resistive paths l4 and 18 can be by laserabrading or any other suitable abrading procedure. This step can beautomated with, for example, a laser abrader automatically removingportions of the resistive paths l4 and 18 until the ratio of each of thepaths l4 and 18 to the path 16 reached a predetermined level,automatically stopping the abrading operation. Each of the fixedresistive paths l4 and 18 contains a wide portion 17 and a narrowportion 19, the wide portion abraded at 77 to increase the resistance ofthat particular resistive path.

Compactness of the voltage divider is achieved by the symmetricplacement of each of the resistive paths l4 and 18 on either side of thearcuate resistive path 16, each of the fixed resistive paths disposedaround the cator holes 34. As best seen in FIG. 4, the driver 23 and theresistive paths 14 and 18 are compactly placed on substrate 12, thedriver 23 overlying approximately one-half the area of the substrate,the resistive paths l4 and 18 disposed on the remaining area of thesubstrate.

While there has been illustrated and described what is at presentconsidered to be a preferred embodiment of the present invention, itwill be appreciated that numerous changes and modifications are likelyto occur totho'se skilled in the a t, and it is intended in the appendedclaims to cover all those changes and modifications which fall-withinthe true spirit and scope of the present invention: i

- What is claimed as new and desired'to be secured by Letters Patent ofthe United States is:

ISA variable voltage divider comprising a dielectric substrate, aplurality of conductive terminations, including one relatively highvoltage termination, supported on said substrate, resistance meanscomprising first; second and third resistive p'aths supported on saidsubstrate, one end of said second resistive p'ath being connected tosaid first resistive pathand the'other end of said second resistive pathbeing connected to said high voltage termination, oneend of the thirdresistive path being connected'to a second one'of the terminations andthe other endof'the'third resistive pathbeing connected to said firstresistive path, a collector supported on said substrate, adjusting meanssupported for tr'ation means comprising a firs't registration means anda secondregistration means spaced apart from said first registrationmeans, said second resistive path being arcuately disposed about one ofsaid registration means and said-third resistive path being arcuatelydisposed about the other'of said registration means. 7 i s I '2. Thevoltage divider of'clairn 1, wherein said first resistive path iscircularly disposed about an aperture provided in said substratedandsaid adjusting means contains a contactor driver supported in saidaperture and overlying said: first resistive path, said contactordriverover lying a'sigiiificant portion of the area of said substrate,said second and third resistive paths being disposed on the" remainingarea of said substrate."

' 3. The voltage divider of claim 2, comprising a housing containinglocator means and provided with an opening and a receptaclecommunicating with said opening, wherein said substrate containsregistration means engageable with said locator means to locate thesubstrate in the housing, and wherein said adjusting means contains acontactor driver disposed in said receptacle, said driver containing afirst surface and a second surface spaced apart from said first surfaceand substantially parallel thereto, said first surface containing anintegral knob portion extending through said opening and said secondsurface containing an integral shaft portion secured in said aperture.

4. The voltage divider of claim 1, comprising a housing and locator pinssecured to said housing, wherein said first registration means is afirst hole at one end of the substrate and said second registrationmeans is a second hole at the other end of said substrate, one of saidlocator pins extending through each of said holes.

5. The voltage divider of claim 4, wherein said housing is provided withan opening and said substrate is provided with an aperture, said locatorpins being disposed in a line with said opening and said locator holesbeing disposed in a line with said aperture, portions of said locatorpins being swaged to the substrate and securing the substrate to thehousing, a portion of said adjustment means extending through saidopening.

6. The voltage divider of claim 5, wherein said housing comprises anintegral bushing and is provided with I an annular bearing. said bearingand said bushing being concentrically disposed about said opening.

7. A variable voltage divider comprising a housing containing locatormeans and a receptacle, a dielectric substrate containing registrationmeans engaging said locator means and locating substrate in the housing,a center aperture, a plurality of conductive terminations supported onsaid substrate, resistance means comprising a first, a second, and athird resistive path supported on said substrate, one end of said secondresistive path being connected to one end of said first resistive path,one end of said third resistive path being connected to the other end ofsaid first resistive path, the other end of said second resistive pathbeing connected to a first one of the conductive terminations, and theother end of said third resistive path being connected to a second oneof the conductive terminations, a collector supported on said substrate,and adjusting means extending into said center aperture and supportedfor movement relative to said substrate, said adjusting means containinga contactor driver overlying said first resistive path, said driverdisposed in the receptacle of said housing, and a conductive contactorconstrained to move with said contactor driver and wipingly engaging thefirst resistive path and the collector, said first resistive pathbeing-circularly disposed about said center aperture in the substrate,said registration means comprising a first registration means and asecond registration means spaced apart from said first registrationmeans, said second resistive path being arcuately disposed about one ofsaid registration means and said third resistive path being arcuatelydisposed about the other of said registration means.

8. The voltage divider of claim 7 wherein said contactor driver containsa first surface, said first surface containing an integral shaft portionsecured in the center aperture of said substrate, said driver overlyingapproximately one-half of the area of the substrate, said sec: nd andthird resistive paths being disposed on the remaining area ofsaidsubstrate.

a DC voltage in the range of 6,000 volts and higher, the dividercomprising a substantially rectangular dielectric substrate containingan aperture centrally located as to one of the width or the length ofthe substrate, the

substrate being provided with a pair of locating holes cally connectedto one end of the arcuate resistor and 9. A variable voltage divider foruse in circuits having the other end of the first fixed resistorbeingelectrically connected to a first one of the terminations, theother end of the arcuate resistor being electrically connected toone endof th e'second'fixed' resistor and the other end of the second fixedresistor being electricallyconnected to a second one of theterminations, the arcuate resistor being disposed between the firstand-second fixed resistors, thefirst fixed resistor and the'second fixedresistor defining a designated resistance ratio, the

resistance ratio between the first fixed resistor and the second fixedresistor being dependent upon the resistance of the arcuate resistor, acollector supported on,

the substrate and circumposing at least a portion of the strate, thediameter of' the driver being substantially equal to the maximum widthof the substrate, a contactor constrained for movement with the driverand wipably engaging the arcuate resistor and the collector for alteringthe voltageibetween the first one. and the third one of theterminations. 10. The voltage divider of claim 9, wherein a' third fixedresistor is disposed between the collector and the third one of theterminations.

1. A variable voltage divider comprising a dielectric substrate, aplurality of conductive terminations, including one relatively highvoltage termination, supported on said substrate, resistance meanscomprising first, second and third resistive paths supported on saidsubstrate, one end of said second resistive path being connected to saidfirst resistive path and the other end of said second resistive pathbeing connected to said high voltage termination, one end of the thirdresistive path being connected to a second one of the terminations andthe other end of the third resistive path being connected to said firstresistive path, a collector supported on said substrate, adjusting meanssupported for movement relative to said substrate, and a conductivecontactor constrained to move with said adjusting means and wipablyengaging the first resistive path and the collector, said substratecomprising registration means for locating the substrate in a housing,said registration means comprising a first registration means and asecond registration means spaced apart from said first registrationmeans, said second resistive path being arcuately disposed about one ofsaid registration means and said third resistive path being arcuatelydisposed about the other of said registration means.
 2. The voltagedivider of claim 1, wherein said first resistive path is circularlydisposed about an aperture provided in said substrate and said adjustingmeans contains a contactor driver supported in said aperture andoverlying said first resistive path, said contactor driver overlying asignificant portion of the area of said substrate, said second and thirdresistive paths being disposed on the remaining area of said substrate.3. The voltage divider of claim 2, comprising a housing containinglocator means and provided with an opening and a receptaclecommunicating with said opening, wherein said substrate containsregistration means engageable with said locator means to locate thesubstrate in the housing, and wherein said adjusting means contains acontactor driver disposed in said receptacle, said driver containing afirst surface and a second surface spaced apart from said first surfaceand substantially parallel thereto, said first surface containing anintegral knob portion extending through said opening and said secondsurface containing an integral shaft portion secured in said aperture.4. The voltage divider of claim 1, comprising a housing and locator pinssecured to said housing, wherein said first registration means is afirst hole at one end of the substrate and said second registrationmeans is a second hole at the other end of said substrate, one of saidlocator pins extending through each of said holes.
 5. The voltagedivider of claim 4, wherein said housing is provided with an opening andsaid substrate is provided with an aperture, said locator pins beingdisposed in a line with said opening and said locator holes beingdisposed in a line with said aperture, portions of said locator pinsbeing swaged to the substrate and securing the substrate to the housing,a portion of said adjustment means extending through said opening. 6.The voltage divider of claim 5, wherein said housing comprises anintegral bushing and is provided with an annular bearing, said bearingand said bushing being concentrically disposed about said opening.
 7. Avariable voltage divider comprising a housing containing locator meansand a receptacle, a dielectric substrate containing registration meansengaging said locator means and locating substrate in the housing, acenter aperture, a plurality of conductive terminations supported onsaid substrate, resistance means comprising a first, a second, and athird resistive path supported on said substrate, one end of said secondresistive path being connected to one end of said first resistive path,one end of said third resistive path being connected to the other end ofsaid first resistive path, the other end of said second resistive pathbeing connected to a first one of the conductive terminations, and theother end of said third resistive path being connected to a second oneof the conductive terminations, a collector supported on said substrate,and adjusting means extending into said center aperture and supportedfor movement relative to said substrate, said adjusting means containinga contactor driver overlying said first resistive path, said driverdisposed in the receptacle of said housing, and a conductive contactorconstrained to move with said contactor driver and wipingly engaging thefirst resistive path and the collector, said first resistive path beingcircularly disposed about said center aperture in the substrate, saidregistration means comprising a first registration means and a secondregistration means spaced apart from said first registration means, saidsecond resistive path being arcuately disposed about one of saidregistration means and said third resistive path being arcuatelydisposed about the other of said registration means.
 8. The voltagedivider of claim 7 wherein said contactor driver contains a firstsurface, said first surface containing an integral shaft portion securedin the center aperture of said substrate, said driver overlyingapproximately one-half of the area of the substrate, said second andthird resistive paths being disposed on the remaining area of saidsubstrate.
 9. A variable voltage divider for use in circuits having a DCvoltage in the range of 6,000 volts and higher, the divider comprising asubstantially rectangular dielectric substrate containing an aperturecentrally located as to one of the width or the length of the substrate,the substrate being provided with a pair of locating holes on oppositeend of the substrate, for locating the substrate in a housing, thecenters of the aperture and the locating holes lying substantially in astraight line, a plurality of conductive terminations supported on thesubstrate, an arcuate resistor and first and second fixed resistorssecured on a surface on one side of the substrate, one end of the firstfixed resistor being electrically connected to one end of the arcuateresistor and the other end of the first fixed resistor beingelectrically connected to a first one of the terminations, the other endof the arcuate resistor being electrically connected to one end of thesecond fixed resistor and the other end of the second fixed resistorbeing electrically connected to a second one of the terminations, thearcuate resistor being disposed between the first and second fixedresistors, the first fixed resistor and the second fixed resistordefining a designated resistance ratio, the resistance ratio between thefirst fixed resistor and the second fixed resistor being dependent uponthe resistance of the arcuate resistor, a collector supported on thesubstrate and circumposing at least a portion of the aperture andelectrically connected to a third one of the terminations, a driver, ashaft connected to the driver and extending into the aperture androtatably supporting the driver for movement relative to the substrate,the diameter of the driver being substantially equal to the maximumwidth of the substrate, a contactor constrained for movement with thedriver and wipably engaging the arcuate resistor and the collector foraltering the voltage between the first one and the third one of theterminations.
 10. The voltage divider of claim 9, wherein a third fixedresistor is disposed between the collector and the third one of theterminations.